Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO2, as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and −1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.

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Three-dimensional ͑3D͒ tungsten oxide nanowire networks have been demonstrated as a high-surface area material for building ultrasensitive and highly selective gas sensors. Utilizing the 3D hierarchical structure of the networks, high sensitivity has been obtained towards NO 2 , revealing the capability of the material to detect concentration as low as 50 ppb ͑parts per billion͒. The distinctive selectivity at different working temperatures is observed for various gases. The results highlight that the nanobelts ͑nanowires͒ technology can be adopted for the development of gas sensors with performances suitable for practical applications.

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